This invention relates to an ink jet recording apparatus for jetting ink drops from nozzle orifices, thereby recording images and characters on recording paper.
An ink jet recording apparatus using piezoelectric vibrators in a vertical vibration mode, which will be hereinafter referred to as recording head, generally comprises a channel unit 1 formed with a large number of nozzle orifices 8 and pressure chambers 7 and a head case 2 for housing piezoelectric vibrators 6, to which the channel unit 1 is attached, as shown in FIGS. 13 and 14.
The channel unit 1 comprises a nozzle plate 3 formed with rows of the nozzle orifices 8, a channel formation substrate 4 formed with rows of the pressure chambers 7 communicating with the nozzle orifices 8, and a vibration plate 5 for blocking lower openings of the pressure chambers 7, the nozzle plate 3, the channel formation substrate 4, and the vibration plate 5 being stacked on each other. The channel formation substrate 4 is formed with an ink reservoir 9 communicating with the pressure chambers 7 via an ink channel 10 for storing ink introduced into the pressure chambers 7.
The head case 2 has a space 12 penetrated up and down for housing the piezoelectric vibrators 6. Each piezoelectric vibrator 6 has a rear end side fixedly secured to a fix board 11 attached to the head case 2 and a tip face fixedly secured to an island part SA on the lower face of the vibration plate 5. In FIG. 13, numeral 14 denotes a frame for protecting the nozzle plates 3, etc.
In the recording head, a drive signal generated by a drive circuit is input to the piezoelectric vibrator 6 via a flexible circuit board 13 for expanding and contracting the piezoelectric vibrator 6 in the longitudinal direction thereof for changing pressure in the pressure chamber 7, thereby jetting ink in the pressure chamber 7 as an ink drop through the nozzle orifice 8.
In an ink jet recording apparatus using the recording head as described above, if print data runs out and the recording head itself is placed in a pause state, ink in the vicinity of the nozzle orifices 8 dries and the nozzle orifices are clogged. Thus, while the print operation is not performed, the recording head is sealed with a cap. However, if the recording head is left sealed with the cap for a long term, the solvent of ink in the proximity of the nozzle orifices 8 is volatilized little by little, the viscosity is increased, and trouble of making it impossible to print at once, degrading the print quality, etc., occurs easily. Further, new ink is supplied in sequence to the nozzle orifices 8 jetting ink drops consecutively by the print operation and the nozzle orifices 8 are hard to be clogged, but the nozzle orifices 8 positioned at the top end, the bottom end, etc., and having an extremely low opportunity of jetting ink drops are easily clogged because ink in the vicinity of the nozzle orifices 8 dries and the viscosity is increased during printing.
To deal with such a problem, as preliminary operation, etc., before print starts, when the recording apparatus is powered on or a print signal is first input, negative pressure is given to each nozzle orifice 8 by a suction pump, whereby ink is forcibly sucked from the nozzle orifices 8, whereby clogging of the nozzle orifices 8 is resolved and the jetting capability of ink is recovered as xe2x80x9ccleaning operation.xe2x80x9d
To perform the cleaning operation, as shown in FIG. 15A, first the margin of a cap 15 shaped like a shallow box opened to the top is abutted against a nozzle face 40 on the lower side of the nozzle plate 3 for sealing. Next, a pump 16 connected to a suction pipe 17 is actuated with a valve 19 of a leak pipe 18 closed for sucking the inside of the cap 15, whereby ink is forcibly sucked from the nozzle orifices 8.
In the recording apparatus, after the ink suction terminates, sucking of the pump 16 is continued with the valve 19 of the leak pipe 18 opened for leaking the inside of the cap 15 and ink accumulating in the cap 15 is discharged. However, in the recording apparatus, when ink in the cap 15 is discharged, air enters the cap 15 from the leak pipe 18 and, bubbles 20 occur in a large amount in the cap 15 as shown in FIG. 15B. The bubbles 20 are deposited on the nozzle face or a back-flow of ink is produced by the action of negative pressure occurring in the recording head or an ink cartridge and the bubbles 20 enter the nozzle orifices 8 and a print failure such that ink drops are not jetted or that the ink drop jetting direction becomes unstable may occur in later print.
It is therefore an object of the invention to provide an ink jet recording apparatus for making it possible to preventing bubbles occurring in a cap after cleaning from adhering to a nozzle face, etc., and stabilize the printing operation.
In order to achieve the above object, according to the present invention, there is provided an ink jet recording apparatus comprising:
a recording head including a pressure chamber to which ink is supplied, a nozzle face provided with a nozzle orifice communicated with the pressure chamber, and an element for generating pressure in the pressure chamber to eject an ink drop from the nozzle orifice;
a cap member for sealing the nozzle face while defining an internal space therein;
a cover member provided in the internal space of the cap member;
a suction member for giving negative pressure to the internal space of the cap member; and
a protrusion formed on the cover member at a portion opposing to the nozzle orifice, so as to face the nozzle face while defining a narrow gap therebetween to cover the nozzle orifice when the cap member seals the nozzle face.
In this configuration, if bubbles occur in the internal space of the cap member at the time of nozzle maintenance such as a cleaning operation, the nozzle orifice is covered by the cover member with the narrow gap in between and thus entering bubbles in the nozzle orifice is almost eliminated. Since ink in the cap member is prevented from back flowing into the nozzle orifice, mixing of inks when a plurality of inks are used is prevented.
Furthermore, since ink is held by the surface tension of liquid sandwiched between the cover member and the nozzle face, so that deposition of bubbles occurring when ink is discharged onto the nozzle face can be effectively prevented without destroying meniscuses. In addition, a jet failure caused by drying the recording head is also decreased. Therefore, a print failure such that ink drops are not jetted or that the ink drop jetting direction becomes unstable is hard to occur in later print.
Preferably, a gap is defined between the cap member and the cover member. An opening is formed within the gap so as to communicate with the suction member.
In this configuration, since the ink is sucked from the opening in the gap while retaining the ink in the nozzle orifice by the cover member when the cleaning operation is performed, a jet failure during the cleaning operation can be avoided by the simple configuration.
Preferably, a top face of a peripheral margin portion of the cap member is higher than a top face of the protrusion.
Preferably, the cover member is provided with a first abutment protrusion which. is to be abutted against the nozzle face to define a gap between the cover member and the nozzle face. The first abutment protrusion is continuously formed so as to surround the protrusion.
The first abutment protrusion may be continuously formed so as to surround the cover member. Here, a second abutment protrusion is formed on a portion surrounded by the first abutment protrusion.
In the above configurations, the ink surface area exposed to the atmosphere is lessened with the cover member covering nozzle orifice with the narrow gap between and, for example, to cover the nozzle orifice with the cover member while the recording apparatus stops, volatilization of ink solvent from the nozzle orifice can be decreased and occurrence of clogging can be prevented. Since the amount of ink held in the gap between the cover member and the nozzle face is lessened with the cover member covering the nozzle orifice with the narrow gap between, deposition of ink onto the nozzle face is lessened and removal of ink on the nozzle face by wiping, etc., is facilitated.
Preferably, the cover member covers the nozzle orifice during quiescent time of the apparatus.
In this configuration, volatilization of ink solvent from the nozzle orifice can be decreased drastically and occurrence of clogging can be decreased remarkably.
Preferably, the cover member is brought into intimate contact with the nozzle face to cover the nozzle orifice.
In this configuration, the hermeticity of the nozzle orifice by the cover member is enhanced and entering bubbles in the nozzle orifice can be prevented effectively.
Preferably, the cover member is made of a material having a stiffness not greater than a stiffness of a material composing the cap member, for example, an elastic material.
In this configuration, the hermeticity of the nozzle orifice by the cover member is enhanced and entering bubbles in the nozzle orifice and back-flow of ink can be prevented more effectively.
Preferably, a face of the cover member to be abutted against the nozzle face includes an inclined face.
In this configuration, the cover member abuts against the nozzle face gradually from the nearest portion of the inclined face to the nozzle face and thus sandwiching ink and bubbles between the nozzle face and the cover member is almost eliminated and back-flow of ink into the nozzle orifice and entering bubbles in the nozzle orifice can be prevented effectively.
Preferably, the suction member gives the negative pressure when the cover member defines the predetermined narrow gap.
In this configuration, ink sucking from the nozzle orifice and ink discharging from the cap member can be executed with the cover member and the cap member held in the same state, so that the structure and control of the: cap member and the cover member can be simplified.
Preferably, a face of the cover member to be abutted against the nozzle face is configured to be a hydrophilic surface.
In this configuration, ink is effectively held between the cover member and the nozzle orifice, so that the adverse effect of destroying meniscuses, etc., is lessened.
Preferably, an inner face of the cap member defining the internal space is configured to be a hydrofuge surface except for the hydrophilic surface.
In this configuration, after ink in the cap member is discharged, ink in the cap member becomes hard to remain.
Preferably, the cover member and the cap member are provided as an integral member.
In this configuration, the structure is comparatively simple and is advantageous in costs and ink leakage, etc., is also hard to occur.